(A) undermines the argument, because it establishes a way that sales can indicate something about success as an underground group. According to (A), if the recordings DO sell either especially well or especially poorly, then the underground rock group is NOT successful as an underground group. We don’t want to establish a connection that allows us to infer, merely from the level of sales, that a group is successful or that a group is unsuccessful.

(B) connects the premises to the idea that sales don’t indicate success as an underground rock group. If, as (B) says, being too trendy indicates lack of success as an undergroup group, then we can’t just look at high sales and infer the group is successful. And if, as (B) says, being incompetent indicates lack of success as an undergroup group, then we can’t just look at low sales and infer the group is successful, either. So neither high sales nor low sales indicates a group is successful as an underground group.

We’re concerned with whether a group is successful “as an underground rock group.” This is different from just being a success. In addition, (C) only helps establish that failing to sell well is not a mark of success. But it leaves open the possibility that selling well might be a mark of success. We want to show both that selling well and selling poorly do not establish success as an underground rock group.

(D) establishes something about the situation in which a group is competent. But the premises don’t involve a situation in which a group is competent. Rather, one of the premises involves a situation in which a group might be incompetent.

(E) establishes something about competent groups and groups that do create authentically underground music. But the premises concern groups that might be incompetent or that might not have created authentically underground music.